package de.pixart.messenger.crypto.axolotl;

import android.support.annotation.NonNull;
import android.support.annotation.Nullable;
import android.util.Log;

import org.whispersystems.libsignal.DuplicateMessageException;
import org.whispersystems.libsignal.IdentityKey;
import org.whispersystems.libsignal.InvalidKeyException;
import org.whispersystems.libsignal.InvalidKeyIdException;
import org.whispersystems.libsignal.InvalidMessageException;
import org.whispersystems.libsignal.InvalidVersionException;
import org.whispersystems.libsignal.LegacyMessageException;
import org.whispersystems.libsignal.NoSessionException;
import org.whispersystems.libsignal.SessionCipher;
import org.whispersystems.libsignal.SignalProtocolAddress;
import org.whispersystems.libsignal.UntrustedIdentityException;
import org.whispersystems.libsignal.protocol.CiphertextMessage;
import org.whispersystems.libsignal.protocol.PreKeySignalMessage;
import org.whispersystems.libsignal.protocol.SignalMessage;
import org.whispersystems.libsignal.util.guava.Optional;

import java.util.Iterator;
import java.util.List;

import de.pixart.messenger.Config;
import de.pixart.messenger.entities.Account;
import de.pixart.messenger.utils.CryptoHelper;

public class XmppAxolotlSession implements Comparable<XmppAxolotlSession> {
    private final SessionCipher cipher;
    private final SQLiteAxolotlStore sqLiteAxolotlStore;
    private final SignalProtocolAddress remoteAddress;
    private final Account account;
    private IdentityKey identityKey;
    private Integer preKeyId = null;
    private boolean fresh = true;

    public XmppAxolotlSession(Account account, SQLiteAxolotlStore store, SignalProtocolAddress remoteAddress, IdentityKey identityKey) {
        this(account, store, remoteAddress);
        this.identityKey = identityKey;
    }

    public XmppAxolotlSession(Account account, SQLiteAxolotlStore store, SignalProtocolAddress remoteAddress) {
        this.cipher = new SessionCipher(store, remoteAddress);
        this.remoteAddress = remoteAddress;
        this.sqLiteAxolotlStore = store;
        this.account = account;
    }

    public Integer getPreKeyIdAndReset() {
        final Integer preKeyId = this.preKeyId;
        this.preKeyId = null;
        return preKeyId;
    }

    public String getFingerprint() {
        return identityKey == null ? null : CryptoHelper.bytesToHex(identityKey.getPublicKey().serialize());
    }

    public IdentityKey getIdentityKey() {
        return identityKey;
    }

    public SignalProtocolAddress getRemoteAddress() {
        return remoteAddress;
    }

    public boolean isFresh() {
        return fresh;
    }

    public void setNotFresh() {
        this.fresh = false;
    }

    protected void setTrust(FingerprintStatus status) {
        sqLiteAxolotlStore.setFingerprintStatus(getFingerprint(), status);
    }

    public FingerprintStatus getTrust() {
        FingerprintStatus status = sqLiteAxolotlStore.getFingerprintStatus(getFingerprint());
        return (status == null) ? FingerprintStatus.createActiveUndecided() : status;
    }

    @Nullable
    byte[] processReceiving(List<AxolotlKey> possibleKeys) throws CryptoFailedException {
        byte[] plaintext = null;
        FingerprintStatus status = getTrust();
        if (!status.isCompromised()) {
            Iterator<AxolotlKey> iterator = possibleKeys.iterator();
            while (iterator.hasNext()) {
                AxolotlKey encryptedKey = iterator.next();
                try {
                    if (encryptedKey.prekey) {
                        PreKeySignalMessage preKeySignalMessage = new PreKeySignalMessage(encryptedKey.key);
                        Optional<Integer> optionalPreKeyId = preKeySignalMessage.getPreKeyId();
                        IdentityKey identityKey = preKeySignalMessage.getIdentityKey();
                        if (!optionalPreKeyId.isPresent()) {
                            if (iterator.hasNext()) {
                                continue;
                            }
                            throw new CryptoFailedException("PreKeyWhisperMessage did not contain a PreKeyId");
                        }
                        preKeyId = optionalPreKeyId.get();
                        if (this.identityKey != null && !this.identityKey.equals(identityKey)) {
                            if (iterator.hasNext()) {
                                continue;
                            }
                            throw new CryptoFailedException("Received PreKeyWhisperMessage but preexisting identity key changed.");
                        }
                        this.identityKey = identityKey;
                        plaintext = cipher.decrypt(preKeySignalMessage);
                    } else {
                        SignalMessage signalMessage = new SignalMessage(encryptedKey.key);
                        try {
                            plaintext = cipher.decrypt(signalMessage);
                        } catch (InvalidMessageException | NoSessionException e) {
                            if (iterator.hasNext()) {
                                Log.w(Config.LOGTAG, account.getJid().asBareJid() + ": ignoring crypto exception because possible keys left to try", e);
                                continue;
                            }
                            throw new BrokenSessionException(this.remoteAddress, e);
                        }
                        preKeyId = null; //better safe than sorry because we use that to do special after prekey handling
                    }
                } catch (InvalidVersionException | InvalidKeyException | LegacyMessageException | InvalidMessageException | DuplicateMessageException | InvalidKeyIdException | UntrustedIdentityException e) {
                    if (iterator.hasNext()) {
                        Log.w(Config.LOGTAG, account.getJid().asBareJid() + ": ignoring crypto exception because possible keys left to try", e);
                        continue;
                    }
                    throw new CryptoFailedException("Error decrypting SignalMessage", e);
                }
                if (iterator.hasNext()) {
                    break;
                }
            }
            if (!status.isActive()) {
                setTrust(status.toActive());
                //TODO: also (re)add to device list?
            }
        } else {
            throw new CryptoFailedException("not encrypting omemo message from fingerprint " + getFingerprint() + " because it was marked as compromised");
        }
        return plaintext;
    }

    @Nullable
    public AxolotlKey processSending(@NonNull byte[] outgoingMessage, boolean ignoreSessionTrust) {
        FingerprintStatus status = getTrust();
        if (ignoreSessionTrust || status.isTrustedAndActive()) {
            try {
                CiphertextMessage ciphertextMessage = cipher.encrypt(outgoingMessage);
                return new AxolotlKey(getRemoteAddress().getDeviceId(), ciphertextMessage.serialize(), ciphertextMessage.getType() == CiphertextMessage.PREKEY_TYPE);
            } catch (UntrustedIdentityException e) {
                return null;
            }
        } else {
            return null;
        }
    }

    public Account getAccount() {
        return account;
    }

    @Override
    public int compareTo(XmppAxolotlSession o) {
        return getTrust().compareTo(o.getTrust());
    }

    public static class AxolotlKey {


        public final byte[] key;
        public final boolean prekey;
        public final int deviceId;

        public AxolotlKey(int deviceId, byte[] key, boolean prekey) {
            this.deviceId = deviceId;
            this.key = key;
            this.prekey = prekey;
        }
    }
}